Value-setting means for printing wheels in postal franking machines

ABSTRACT

A franking machine having a printing head in which the values to be printed are manually selected by the rotation of valueselecting wheels, one for each printing wheel, by way of a toothengaging pinion integral with each value-selecting wheel and in which each toothed wheel is provided with an axial bore with gear teeth therein, which are engaged by a pinion integral with a coarse helical screw having a cooperating nut thereon. Each printing wheel is provided with a pinion which engages a toothed rack joined to each nut by a bar passing through the bore in the toothed wheel. The axes of rotation of the value-selecting wheels, the toothed wheels and the coarse helical screws are all parallel to the axis of rotation of the printing head, while the axes of rotation of the printing wheels is transversal of the axis of rotation of the printing head.

for each printing engaging pinion integral with each in which each to g a printing head in which the values to be printed are manually selected by the rotation of value wheel value othed wheel is progear teeth therein, which are en- 945 Sageretal............. 9S0 Rouan et al..... 950 Ryan et 952 Rouan etal................... 953 Lambert...... 955 Komusin 12/1955 Komusin Primary Examiner-Williarn B. Penn Attorney-Holman & Stern -selecting wheels, one by way of a toothselecting wheel and lltllltl ABSTRACT: A franking machine havin 101/91, 1 l0 vided with an axial bore with I United States Patent Inventor James Woodhead Leclllade, England [21] Appl. No. 750,823 [22] Filed Aug. 7,1968 [45] Patented June 29,197! [73] Assignee Roneo Limited Surrey, England 32 Priority Aug. 17, 1967 [33] Great Britain [3 l] 37992/67 [54] VALUE-SETTING MEANS FOR PRINTING WHEELS IN POSTAL FRANKINGMACHINES 2 Claims, 12 Drawing Figs. [52] U.S.Cl.............

rew having a g wheel is provided with k e printing joined to each nut by a g wheels, the toothed wheels and all parallel to the axis of rotation while the axes of rotation of th f o s e x a e h T a .w w m w e m mn o a mm f mnf O n h .m m a h .1 a .m m e lE mm m Ema-D ES f eew o e m l mfw efl a im m s m ntnuafle .w o c w whmefi n W vmmmm h ti. anw f n Y wflb mmm s ei- .loe e h om me m 30 3O :1 cabrmow 4 1 l 2 2 259 9 l 1 cl .1. 5 0 1193 11 4 2 B 9 9 0 1 S m3 T "9 N m E .n P m C E .m N u e m m m mm m m m m m. m R w 0 m n. 4 N% m M U 1 u 7 l c m t" R -I n 4 .I. F .6 w l l l 11 0 6 9 5 5 5 l .l. .l

rotation of the printing head.

2,141,119 12/1938 Wheelereta|......:::.:.....

PATENTEU JUH29 IBYI SHEET 1 BF 9 PATENTED JUNZS I97! 5 9 2 1 sum 2 0r 9 JAMES WOODHEAD 49) PATENTEU JUN29 l9?! SHEET 3 1F 9 kid [Wrap y JAMES WOODHEAD PATENTED JUNZ 9197i SHEET 5 OF 9 //VV[/V70P JAMES WOODHEAD VALUE-SETTING MEANS FOR PRINTING WHEELS IN POSTAL FRANKING MACHINES BACKGROUND OF THE INVENTION The invention relates to franking machines of the kind which besides being capable of franking envelopes, is adapted to provide printed labels for attachment to postal packets which cannot be inserted into the machine for franking in the normal way, while the object of the invention is to provide a franking machine of the kind above referred to, which is positive in action, and is more reliable in use than machines heretofore proposed.

SUMMARY OF THE INVENTION The invention consists in a franking machine having a printing head in which the values to be printed are manually selected by the rotation of value-selecting wheels, one for each printing wheel, by way of a tooth-engaging pinion integral with each value-selecting wheel, characterized in that each toothed wheel is provided with an axial bore with gear teeth therein, which are engaged by a pinion integral with a coarse helical screw having a cooperating nut thereon, each printing wheel being provided with a pinion which engages a toothed rack joined to each nut by a bar passing through the bore in the toothed wheel.

The invention further consists in a franking machine as set forth in the preceding paragraph in which the axes of rotation of the value-selecting wheels, the toothed wheels and the coarse helical screws are all parallel to the axis of rotation of the printing head, while the axis of rotation of the printing wheels is transversal of the axis of rotation of the printing head.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings show, by way of example only, one embodiment of the invention in which:

FIG. I is a view in perspective of the label paper feed mechanism;

FIG. 2 is a view in perspective of the other side of the frame illustrated in FIG. ll;

FIG. 3 is 'a view in perspective, partly broken away, of slogan control;

FIG. 4 is a view in perspective of the interlock;

FIG. 5 is a perspective view of the clutch with the outer ring removed for clarity;

FIG. 6 is a perspective view of the value change mechanism;

FIG. 7 is a perspective view ofthe meter locking means;

FIG. 8 is a general perspective view of the machine showing the relationship of the mechanism shown in FIGS. 1 to 7;

FIG. 9 is a view in perspective along the lines of FIG. 8 illustrating the manner in which the printing head is driven, via a clutch, by an electric motor;

FIG. 10 is a diagrammatic view in elevation of the mechanism for changing the position of the printing wheels;

FIG. III is a view taken along line II-II of FIG. 10, the view looking in the direction of the arrows; and

FIG. 12 is a view taken along line 12-12 of FIG. 10, the view looking in the direction of the arrows.

DETAILED DESCRIPTION OF THE INVENTION It may be seen from FIG. 8 that the machine comprises a hollow boxlike base member A which forms a common support for the internal mechanism of the machine. There is provided a horizontal plate B, upon which, at the nearer end, the piece of mail to be franked is placed, and along which it is conveyed to pass under a printing head C.

The printing head C is driven by an electric motor, mounted below a clutch D, and connected thereto by a gear drive (FIG. 9). The motor runs continuously and the drive is initiated by the clutch D during each cycle of operation.

The value to which the printing wheels in the head C are selected by means of selector wheels, of which one B is shown.

To ensure that the total of the values printed are correct and no errors can be introduced, the register meter is locked by means of a pawl and cam mechanism. F.

Besides franking pieces of mail such as envelopes, the machine is adapted to print upon labels cut from a roll of paper G. The paper strip is fed to the printing head C by a feed and cutting mechanism H which is adapted to provide labels of two different lengths, and also to control the printing of a slogan or otherwise advertising display upon each label at the choice of the operator of the machine.

The mechanism of the machine is protected by a cover I which is removable for servicing of the machine.

The features of the machine above referred to are each described in detail hereinafter with reference to the respective FIGS. 1-7.

The label paper feed mechanism and the slogan control and interlock device are provided in order that one can obtain long or short labels according to the setting ofa hand control, and includes means for suppressing the printing of the slogan or advertising display when short labels are selected.

FIG. 1 shows a main bearing side frame 34 with the nearer part of the mechanism in view, and FIG. 2 shows the assembly on the other side of the main frame. A drum 1, FIG. 2, is mounted integrally on the shaft 5, as also is disc 3 which has two notches 3A cut to The drum I is of such diameter that its periphery is equal to the length of along label. Half its periphery is equal to a short label. By operating a handset lever 35 a cam shaft 30 can be rotated, raising and lowering levers 26 and 28 respectively. The bearings of pressure rollers 25 and 27 are mounted in these levers so that the rollers are lifted clear from the drum 1 for purposes of loading the machine with paper. The free end of a roll of paper on a mounting, not shown, is threaded around the drum 2 and over a seesaw" pallet 23. The pressure of rollers 25 and 27 is then restored.

With the power switched on, a gear 36 rotates continuously. A clutch sprag 2 rotates with this gear and is pivotally mounted on a stud 37 which is integral with the gear 36. The gear 36 is free to move around the shaft 5. A tooth 2B of the sprag 2 would engage in the notch 3A in the disc 3 but for the presence of a lobe 4 on lever 11. The top end of lever 11 passes through side frame 34, FIG. I, having a slotted hole and a strong spring 22 urging it to the right hand of the figure as shown. The spring 38, FIG. 2, is not strong enough to overcome the pressure existing at the lobe 4, and so that the tooth 28 on sprag 2 would jump" or ride clear of the notch 3B in disc 3. Similarly, the presence of a double-lobed cam 9 on shaft 10 prevents engagement of the sprag in second and 180 opposite notch. No drive will therefore be transferred to the drum shaft 5.

Drum shaft 5 comes through a disc 13 with a grooved hub which is capable of being moved laterally to-and-fro having a key, not shown, which engages with a slot in the shaft 5. The disc 13 therefore revolves with the drum 1 and shaft 5. Disc 13 has four pins, two long ones 15, one not being visible, and two short ones 14. These pins 14 and 15 engage in radial slots 16A in a Geneva wheel 16. The Geneva wheel 16 is fixed to the shaft 10, which is integral with cam 9, see FIG. 2, and knife assembly 7.

The knife assembly 7 has a double-edged blade 7A (only one side of which is shown) with sharp V-shaped points at two opposite 180 apart. The drum 1 has two inserts 73 diametrically opposite (only one of which is shown) which have V grooves exactly complementary to the serrations of blade 7A. These two inserts 73 are locked into drum 1, but have springs underneath urging them outwards. The blade 7A is of such a size as to interfere slightly piercing the label paper to the maximum extent. Damage to the insert is avoided because of the give in the spring insert.

In FIG. 6 there is illustrated the mechanism for changing the printing wheel within the printing head C with a change of setting of the value required to be printed by the selective wheel 201. While this figure illustrates but one such selective wheel 201, it is to be understood that a selective wheel 201 is provided for each printing wheel and each selective wheel is operated by a similar mechanism from the Geneva wheel 16. In this position, short pins 14 cannot engage in the slots 16A of the Geneva wheel 16.

The action which occurs on the demanding ofa long" label is as follows:

A slide 12, FIG. 1, has a slotted hole behind washer 39. The slide can therefore be moved by hand operation to the left by a thumb knob not shown, with stepped end at 40 also carrying lever 11 to the left. Lobe 4, FIG. 2, ceases to influence sprag 2 which now engages disc 3 and rotates the shaft 5 with the drum 1 in a counterclockwise direction. After 90 only of revolution, the pin 15, FIG. I, on the underside of disc 13 approaches one of the radial slots in the 16A Geneva wheel 16.

During the next 90" of revolution, Geneva wheel 16 is rotated also through 90, taking with it shaft 10, cam 9 and the knife blade assembly 7. By virtue of the cam 9 rotating in a clockwise direction, it clears lobe 2A of sprag 2, thus allowing sprag 2 to continue driving disc 3. Should the hand operation of slide 12 have been unnecessarily prolonged, no repeat can occur while slide 12 is raised clear of lever 11 by the action of pins 15 as they revolve with disc 13.

The drum 1, shaft 5 and disc 13 continue to rotate until sprag 2 has again become engaged by the restored presence of lobe 4 and lever 11. During the last 90 of revolution, the pin 15, FIG. 1, will have passed the Geneva wheel 16 causing blade 7A, FIG. 2, to become engaged with the paper and the insert 73 in drum 1. The paper becomes perforated severely, but not quite separated. At the moment of piercing, the leading edge of the paper has entered the first feed rolls of the printing head feed, not shown, and is pulled tightly over the pallet 23, FIGS. 2 and 4. This member is mounted on a single shouldered stud which is offset, so that when the paper tightens thereover, it seesaws raising one side. This occurs when the perforation passes over it, thus triggering off a tear, which is then easily completed by the tug of the feed rolls.

The paper thus is separated before it passes under the franking head. The length of paper is equal to the total circumference of the drum 1. In this setting, it is assumed that a slogan or display is to be printed. Feed rolls 60 and 61 carry the label forward to the printing drumhead, and have thereabove, as shown in FIG. 4, flexible pressure bands 62 and 63, which are pressed downwards by spring 64 betweensupport bracket 65 and carriage 66. The rotation of the printing drum head is initiated by the contacting of the arm of a switch 67, either by a label, when these are being used, or by an envelope when it is inserted into the pinch or nip of the roll 60. A roll 60 of paper strip is housed in a means 69 in the side of the machine, and passes over guide pins, 70, 71 and 72 and thence around the feed drum 1 as previously described. The method of demanding the slogan printing automatically is now described:

In FIG. 3 is seen the part of a printing drum head 42 provided with a slogan die carrier 41. The carrier 41 is pivoted at 43, and its underside rides on cam 44, mounted on shaft 49, while also on shaft 49 are two wheels 47 and 48, each having two teeth projecting at 180 opposite. These wheels are set at 90 to one another. As previously mentioned in ,the description relating to FIG. 1 for demanding a long label, the plate 28 and the lug 20 do not close the microswitch 19. Therefore, the electrical circuit is not closed and electromagnet 50, FIG. 3, is not energized. The armature therefore is at rest in the position shown.

When the printing head is operated, it revolves counterclockwise. The lower extremity of armature 51 lies in the path of wheei 47, and as it sweeps past it will be revolved in a clockwise direction, turning shaft 49 through 90 raising the slogan die carrier 41 by means of the cam 44. This is retained by springs 46. A die 41A mounted on the carrier 41, is now in its raised or printing position, and will remain so, during further cycles of operation, because the tooth of wheel 47 is over to the right hand. Also, because the shaft 49 has been moved through 90", tooth 52 of the nearer wheel 48 is now around in a position where it will engage the tip of armature 51 should the magnet 50 become energized.

The setting of a short label is now described in reference to FIG. 1. The control knob, 74 is operated and turns the cranked rod 17 through to bring the lug 20 around to close the microswitch 19 which causes the operation of the electromagnet 50, FIG. 3. The disc 13, FIG. 1, moves nearer to the Geneva wheel 16. The short pins 14 now operate in the radial slots 16A of the Geneva wheel 26, in addition to the long pins 15. With the hand operation of slide 12 which pushes lever 11, this operates the sprag 2, FIG. 2, after the manner previously described, and the drum 1 revolves. During the first 90 of rotation, pin 14 moves the Geneva wheel 16, shaft 10 and knife assembly 7, FIG. 2, and also cam 9. During the next 90 of rotation, the Geneva wheel 16, FIG. 1, is again moved. The result of this repeated operation in the first 180 of revolution of drum 1, FIG. 2, is that the cam 9 now presents a high portion in the path of sprag 2 and also the knife assembly 7 serrates the paper. Sprag 2 is disengaged from the disc 3 and drum 1 comes to rest after 180 movement only. Enough paper feed only for a short label is half the circumference of the drum 1. The paper is parted as before described. The slogan die 41A does not print ink on the impression roller because the magnet armature 51, being attracted, has caused wheel 48 to turn shaft 49 and cam 44 back to low position.

In FIG. 1, detent spring member 21 retains the Geneva wheel 16, so that it remains in the true position for the entry of the pins 14 and 15. The plate 18 is so shaped that the slide 12 can only be operated in the correct settings of shaft 17. Detent member 31 retains drum 1 and shaft 5 in the true at rest position and avoids overthrow when the sprag 2 is disengaged.

The printing head C is driven by an electric motor, FIG. 9, by way of clutch D. The motor runs continuously while the machine is in use, and each franking process is initiated by the engagement of the Clutch D. The clutch is operated remotely, and it is of vital importance that the printing and recording head should make one revolution and that it should be arrested at a precisely predetermined position, and be prevented from rotating further until demanded to do so by the remote control.

Details of the clutch are shown in FIG. 5 in which outer toothed ring 101 is shown separated, so that the pawl mechanism housing may be clearly seen. The outer ring 101 is driven continuously by the electric motor and fits freely over pawl housing 103 which contains and retains four driving pawls 104a, lllb 1040 and 104d, each of which is urged in an outward direction by a spring, not shown, under each pawl. Screws 106 secure pawl housing 103 to drive plate 102, and also secure pawl housing 103 and drive plate 102 to the end face of a printing/recording head shaft, not shown, which is required to make only one revolution before being arrested by means of projections 109 and 110 being caught under hooked end of pawl 111. A pawl control plate 105 is located between pawl housing 103 and the drive plate 102, and is free to move radially by a predetermined amount, in relation to drive plate 102 and pawl housing 103. Pawl control plate 105 is cutaway internally to provide four internal cam faces 107a, 107b 107C and 107d of which only the first can be seen, and each of which engages a projection provided on the inner face on the four driving pawls 104a 104b 104s, and 104d, retained in the slots in the pawl housing 103.

A trigger stop 111 is pivoted on a shaft 118 and the hooked end of this trigger stop is urged away from the clutch components 102, 103, and 105 by a torsion spring 112.

When the shaft to which the pawl housing 103 and drive plate 102 are rigidly attached, is required to make one revolution, an electric current passing through coil 114 energizes magnet 113, which then attracts the horizontal portion of armature 225, pivoted on shaft 116, thereby withdrawing the top end of the vertical portion of armature 225 from under a projection 1 19 on trigger stop 111.

When the top end of armature 115 is withdrawn from under the projection 119 on trigger stop 111, torsion spring 112 causes the hooked end of trigger stop 111 to move away from the projection 110 on drive plate 102.-

One end of spring 108 is secured to pawl plate 105, and the other end of the spring is secured to drive plate 102. When the hooked end of the trigger stop 111 is withdrawn from projection 109 and projection 110, spring 108 causes pawl plate 105 to rotate in a clockwise direction to the limit provided by an internal stop, and the internal 'cam faces 107a, 107b, 107s, and 107d, in pawl control plate 105 permit the four driving pawls 1041a, 104b, 104s, and 104d to be urged upwards and outwards, each by its own spring, not shown, against the inner toothed bore of outer ring 101.

The pawls 104a, 104b, 1040, and 104d, are unequally spaced around pawl plate 103, and are positioned in such a manner that only one of thefour pawls 1040, 104b, 104c and 104d, can locate against any one of the internal ratchet teeth in the outer ring 101. v

The pawls are spaced so that the radial difference between each pawl is equal to onefourth of the pitch of the internal teeth in outer ring 101. If, therefore, one pawl just misses contact with the radial face of any one of the internal teeth in outer ring 101, the next pawl will engage one-fourth of a pitch of the internal teeth in the outer ring 101 later.

When any one of the pawls104a, 104b, 104c and'104d engage in any one of the internal teeth in outer ring 101, the constantly rotating outer ring 101 drives the printing head via one of the pawls and causes the printing head to rotate.

When the hooked end of trigger stop 111 is withdrawn from projections 109 and 1 10, the pointed end of trigger stop 111 is advanced towards the peripheries of pawl control plate 105 and the drive plate 102, the pointed end of trigger stop 111 advances to within an appropriate distance such that when during the rotation of the printing head the projections 109 and 110 impinge on the pointed end of trigger stop 111, the projections 109 and 110 cause trigger stop 111 to partially rotate around its spindle 118, and cause hooked end of trigger stop 111 to be placed in the path of projections 109 and 110.

The vertical portion of armature 115 is urged by torsion spring 117 against the projection 119 of trigger stop 111. When the hooked end of trigger stop 111 is urged inwards by projections 109 and 110, pushingthe tail end of trigger stop 111 forward, the extreme end of the vertical portion,of armature 225 is able to move under projection 119, on the backface of trigger stop 111, and hold this component in such a position that the hooked end trigger stop 111 is held firmly in the path of the rotating projections 109 and 110.

At the commencement of rotation of the shaft, the projection 109 has been moved radially out of line with respect to the projection 110 by virtue of the spring 108 which is secured at one end to the pawl plate 105 and at the other end to the drive plate 102 rotating by a small amount. Consequently, the projection 109 can reach the underside of the hooked end of trigger stop 111 in advance of the projection 110 on the drive plate 102 and when the projection 109 meets the undersurface of the hooked end of the stop 111, the projection is arrested in such position and thus causes the slots 104', 104", 104" and 104 in the pawl control plate 105 to be rotated out of line with the slots in the pawl housing 103. This action forces downwardly the pawls 1040, 104b, 104c ,and 104d into the pawl housing whereby the projecting rim of the plate 105 retains the pawls in their downward position and out of en gagement with the internal teeth in the outer toothed ring 101. Drive plate 102 continues to rotate until the projection 110 also contacts the undersurface of the hooked end of trigger 'stop111.

FIGS. 6 and 10 to 12 show the mechanism for changing the position of the printing wheels within the printing head C with change of setting of the value required to be printed by means of selector wheel 201, only one is shown in FIG. 6, while in fact one is provided for each printing wheel (see FIGS. 10 and 11), each operated by a similar mechanism.

When a value selecting wheel 201 is rotated by an appropriate amount, to change the value to be printed upon a piece of mail passed through the machine, printing wheel 210 prints a value identical with the number selected. It will be observed that the value selector wheel 201 and the printing wheel 210 rotate about axes which are at right angles to one another.

The value selecting wheel 201, which has on one face pinion 202 and on the other face a projecting drum on the periphery of which are numerals indicating values required to be printed, is one of a number of wheels mounted coaxially with one another, and each meshes with the teeth on the periphery of a disc 204, coaxial with one another, and rotates it by an appropriate amount. Each disc 204 engages its internal teeth 211 with a gear 212 on the end of a screw 205 provided with one or more coarse helical grooves.

A nut 206 with a corresponding thread is located on the screw 205, and moves along the latter with rotation of the value selecting wheel 201. There is a screw 205 for each wheel 201 and disc 204, which are spaced circumferentially around the axis of the disc 204. A rack 207 is provided for each nut 206 and has a tooth portion 207A and a bar portion 207B integrally connected therewith. The bar portion 2078 is attached to the nut 206 by a screw 208 .and the teeth of the tooth portion 207A mesh with a pinion 209 of a printing wheel 210. All printing wheels are on the same axis (FIG. 10).

The gear ratio of pinions 202, discs 204, screws 205, and toothed portions 207A of the racks1207 and pinions 209, are so chosen that when the value selecting wheel 201 rotate a corresponding amount precisely related to the amount of rotation 'of the value selecting wheels 201.

One or more of the mechanisms illustrated in FIG. 6 may be used in each postal franking machine allowing a plurality of value-selecting wheels 201 to be used independently or collectively to operate one or a plurality of printing wheels 210.

in FIG. 7, there is shown a locking mechanism associated with the register meter, which indicates the total value which has been printed by a machine, and is provided in order to prevent errors in the readings given. The printing head is provided in known manner with a toothed wheel, in which the number of teeth which project are caused to correspond to the value to which the associated printing wheel is set. The means for permitting radial movement of the teeth is by a cam track and pins and reference is made to U.S. Pat. No. 2,727,687.For example, in FIG, 7 there are four teeth projecting, of which the last tooth is tooth 301. Consequently, when the printing head is rotated in an anticlockwise direction during the franking process, gear 302 is moved four teeth, with the tooth 301 having just left the gear 302. The gear 302 engages the gear beside the numbered drum and the latter has just moved four units.

In order to prevent any overthrow taking place after the least tooth 301 which is at all times the last tooth to pass the intermediate transfer gear 302 which engages with a gear integral with the value recording wheels 309 hasleft the gear 302, a disc 303 is provided with a cam 303A thereon, which engages follower 304A on a lever which is fixed to the shaft 307, on which there is also provided a lever 306 with a pin 305, which engages the back of pawl 308, and positively prevents further rotation of the gear 302. Prior to the last tooth 301 passing gear 302, the pawl 308 is held in mesh by spring 310. The timingof the cam is such that the pawl 308 commences to engage between two teeth of the gear 302 before the last rising tooth 301 has left the gear 302, thus ensuring that no overthrow is possible.

It is to be understood that the above description is by way of example only and that details for carrying the invention into effect may be varied without departing from the scope of the invention claimed.

lclaim 1. A franking machine of the type having a rotatable printing head in which the values to be printed are manually selected, comprising rotatable printing wheels, a value-selecting wheel for each printing wheel rotatably mounted and the manual rotation of such selecting wheels the values to be printed, a pinion integral with each value-selecting wheel, a rotatable disc having external teeth in mesh with each pinion, each disc having an axial bore provided with internal gear teeth, a coarse helical screw provided with an integral pinion in mesh with the internal gear teeth of each disc, a nut threadedly engaging each screw, a pinion for each printing wheel, a rack having a toothed portion and a bar portion integrally connected thereto, the teeth of the toothed portion meshing with a respective printing wheel pinion, and the integral bar portion passing through the axial bore of the discs and secured to a respective nut.

2. The franking machine as claimed in claim 1 wherein the axes of rotation of the value-selecting wheels, the discs and screws are all parallel to the axis of rotation of said printing head, with the axis of rotation of said printing wheels being transverse with respect to the axis of rotation of the printing head. 

1. A franking machine of the type having a rotatable printing head in which the values to be printed are manually selected, comprising rotatable printing wheels, a value-selecting wheel for each printing wheel rotatably mounted and the manual rotation of such selecting wheels the values to be printed, a pinion integral with each value-selecting wheel, a rotatable disc having external teeth in mesh with each pinion, each disc having an axial bore provided with internal gear teeth, a coarse helical screw provided with an integral pinion in mesh with the internal gear teeth of each disc, a nut threadedly engaging each screw, a pinion for each printing wheel, a rack having a toothed portion and a bar portion integrally connected thereto, the teeth of the toothed poRtion meshing with a respective printing wheel pinion, and the integral bar portion passing through the axial bore of the discs and secured to a respective nut.
 2. The franking machine as claimed in claim 1 wherein the axes of rotation of the value-selecting wheels, the discs and screws are all parallel to the axis of rotation of said printing head, with the axis of rotation of said printing wheels being transverse with respect to the axis of rotation of the printing head. 